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Cell Specialization/Transcript
Transcript A man, Tim, looks into a microscope. Text reads: The Mysteries of Life with Tim and Moby. The text of a letter appears at the end of Tim's microscope. Tim reads it. TIM: Huh. Dear Tim and Moby, how are cells different? From, Steven. Tim and Moby address the camera. TIM: Well, for starters, there are two basic types of cells: prokaryotic and eukaryotic. A split image shows the cross section of a prokaryotic cell on the left and the cross section of a eukaryotic cell on the right. The prokaryotic cell has a thin outer layer, an inner layer, and a central layer. The eukaryotic cell has a thin outer layer, an inner layer, a central layer, and a spherical core. Within the inner layer are five different objects. One resembles thick leaves piled on top of each other, another has an oblong shape with dark and light areas, another has a maze-like pattern and is connected to the spherical core, another is a plain sphere, and the last looks like a cluster of spheres inside a small circle. TIM: Prokaryotic cells don’t have any membrane around their nuclear material. The split image changes to show a whole prokaryotic cell on the left and the back of Moby on the right. The prokaryotic cell looks like an oval with a thin, squiggly tail. TIM: They're single-celled organisms that can live on their own. (Moby puts a pile of slime in Tim's hand.) Thanks a lot. TIM: Eukaryotic cells are what we’re made of. They have a nucleus of hereditary material that’s surrounded by a membrane and controls the life of the cell. The cross section of a eukaryotic cell is shown again. The spherical core is highlighted. TIM: Plant and animal cells are both eukaryotic. A split screen shows two images of cell cross sections. The right image is labeled “animal cell” and consists of the previously described eukaryotic cell. The left cell is labeled “plant cell.” It has a thin outer layer and an inner layer. Within the inner layer are multiple spheres and oblong objects with light and dark areas. A larger shaded area with irregular edges is in the center. Another object in the inner layer is identical to the object in the center of the eukaryotic cell. This consists of a central layer with a spherical core that is attached to a small, maze-like object. TIM: Cells come in all different shapes and sizes. The size and shape of a cell can sometimes tell you something about its job. Four images of cells appear. One is capsule-shaped and has many hairlike appendages. Another is a cross section of the previously described plant cell. Another has an oblong shape with a depression at its center. The fourth consists of several tubular segments connected by a flexible strand. The ends of the strand have branch-like appendages. TIM: One nerve cell in your leg can be a meter long! Those little “fingers” on each end, called dendrites, let signals jump from one nerve synapse to the next. The camera pans across the cell with connected segments. It zooms in on the ends of the cell, and lightning bolts appear between the branchlike appendages to represent firing signals. TIM: This here red blood cell is about one-tenth the size of a period on your computer screen. It’s a tiny flexible disk that can move through even the narrowest blood vessels. The image changes to the oblong cell that has a depression in its center. The camera pulls out to show many of these cells flowing between an upper and a lower wall. TIM: A plant xylem cell is long and hollow with holes so it can transport water and minerals through the plant. The image changes to a tree standing in a grassy lawn. The screen splits to show the tree on the right and a xylem cell on the left. The xylem cell has a prismatic shape and has lines along its side and holes through the interior. TIM: Plant and animal cells are pretty similar inside but there are two major differences. Moby addresses the camera. He holds up a leaf in his right hand and an egg in his left hand. TIM: Plant cells can make their own food, and animal cells can’t. The scene changes to reshow the split screen with the cross sections of plant and animal cells. TIM: Plant cells’ green color comes from green organelles called chloroplasts. Chloroplasts trap light energy and enable plants to conduct photosynthesis. The image of the animal cell disappears, and the plant cell turns on its side. One of the spheres within the inner layer detaches from the cell and moves toward the camera while the rest of the cell moves away. TIM: Animal cells are surrounded with a flexible cell membrane. Plant cells have a membrane too, but outside of that, they protect themselves with a stiff outer wall. Moby stands between two large blobs. He is able to put his hand through the blob on his left. He presses against the object on his right, but he can’t put his hand through it. TIM: Both plant cells and animal cells work in teams. When you take a tiny piece of a plant there are tons of cells clustered together in that piece working together. A split screen shows a grouping of plant-cell cross sections on the left and animal-cell cross sections on the right. TIM: Same goes for a piece of an animal. Tim and Moby address the camera. MOBY: Beep. TIM: I’m not saying that. MOBY: Beep. TIM: Oh fine… Moby hugs Tim. TIM: Cells team up and work together, just like Moby and me. Category:BrainPOP Transcripts